Because it sells out in about 10 minutes each morning. You have to have a strategy set up for calling, and have lightening fingers and lots of pixie dust.
But honestly, did you arrange for PSB instead? Or Cinderellas Gala Feast for dinner? The reviews of CRT are usually less than enthusiastic, but for some reason people are so hyped about getting it... if your little ones truly want to see the Princesses, do one of those in the meantime and keep checking. We LOVED the PSB, I'm sure your children will be thrilled with anything!